Liquid smoke compositions (also known as liquid smoke solutions, and colloquially referred to as liquid smokes) were developed from pyrolysis of hardwood sawdust as a replacement for smoking of food by direct contact with smoke in a smokehouse. Liquid smoke compositions have become a standard industry practice.
Liquid smoke compositions, when applied to the surface of meats, such as various types of sausages, frankfurters, bolognas, beef rolls, hams, and the like, and other proteinaceous foodstuffs, provide a smokey flavor and a dark smoke color to the foodstuff, achieving a smokehouse-like product. Nevertheless, this requires control and balancing of many variables such as the food composition, temperature, humidity, processing time, contact time, amount of liquid smoke, and concentration of liquid smoke.
As is well known to those skilled in the art, liquid smoke compositions obtained from pyrolysis of hardwood sawdust contain constituents primarily from the thermal degradation of cellulose, hemicellulose, and lignin. More particularly, the liquid smoke compositions contain a wide array of over 400 chemical compounds, and hence, liquid smoke compositions are characterized by their content of certain classes of compounds, namely, acids (% titratable acidity), phenols, and carbonyls.
The acids are preservatives and pH control agents. Commercial liquid smoke compositions typically have a pH under about 2.5, and more typically under about 2.3, and a % titratable acidity by volume from about 3% to about 18%.
The phenols give a smokey flavor, and also aroma, to liquid smoke compositions, which typically have a phenols content from about 10 to about 45, and more typically, from about 14 to about 30 mg/ml. The carbonyls impart the brown color to liquid smoke compositions. The phenols and the carbonyls can be measured as described in U.S. Pat. No. 4,431,032 issued Feb. 14, 1984 to Nicholson, assigned to Union Carbide Corporation, which describes techniques for the removal of an undesirable tar component from liquid smoke compositions. Also, the browning potential of liquid smoke compositions can be measured by the well-known in the art Browning Index procedure described in U.S. Pat. No. 4,994,297 issued Feb. 19, 1991 to Underwood, assigned to Ensyn Engineering Associates, Inc., (which describes general background on techniques for the manufacture of liquid smoke compositions including the technique of fast pyrolysis of wood or cellulose), or by the well-known in the art Stain Index procedure involving reaction of liquid smoke with glycine. It is noted that the acids and carbonyls are secondary in contributing to the smokey flavor of liquid smoke compositions.
As the advent of liquid smoke compositions has significantly improved meat processing, attempts have been made to create a liquid smoke product that can impart browning to a foodstuff, but impart minimal or no flavoring. Thus, the foodstuff treated with such a liquid smoke browning would look like a smoked foodstuff, i.e., have a roasted, conventional oven-cooked look, even though the treated foodstuff would not taste smokey like a smoked foodstuff but rather retain its original flavor or have a nondescript, conventional oven-roasted flavor.
Of more particular interest in relation to the present invention is the process of U.S. Pat. No. 5,292,541 issued Mar. 8, 1994 to Underwood et al., assigned to Red Arrow Products Company, Inc., which discloses a process for producing a liquid product for coloring and flavoring a foodstuff by pyrolyzing sugars and starches. The liquid product is useful for imparting a brown smoked color to a foodstuff without adding strong smoked flavors to the foodstuff.
Also, U.S. Pat. No. 5,270,067 issued Dec. 15, 1993 to Underwood et al., assigned to Red Arrow Products Company Inc., is a Continuation-in-Part of an application that matured into U.S. Pat. No. 5,039,537 issued Aug. 13, 1991 to Underwood, assigned to Red Arrow Products Company Inc., and '537 is a Continuation-in-Part of an application that matured into the above-noted '297. Both '067 and '537 disclose a high browning liquid composition made from sugar, starch, monosaccharide, disaccharide, trisaccharide, starch hydrolysate, cellobiose, hemi-cellulose and mixtures thereof ('067) or made from wood or cellulose ('537). Likewise U.S. Pat. No. 5,252,188 to Stradal et al., assigned to Red Arrow Products Company Inc., discloses a high browning liquid composition made from cellulose, wood, sugars, or starches.
Moreover, U.S. Pat. No. 5,395,455 issued Mar. 7, 1995 to Scott et al., assigned to Energy, Mines and Resources--Canada, discloses a process for the production of anhydrosugars from lignin-containing and cellulose-containing biomass by pyrolysis. Significantly, not only is the material that is subjected to pyrolysis not delignified, but also, there is no disclosure of the use of a produced anhydrosugar as a browning agent.
Additionally, U.S. Pat. No. 5,769,934 issued to Ha et al. on Jun. 23, 1998, assigned to FMC Corporation, discloses a representative method for producing microcrystalline cellulose which includes subjecting a cellulose source material to steam explosion treatment. Microcrystalline cellulose is disclosed as being a well-known material that finds widespread use in pharmaceuticals and in foods, e.g., as a stabilizer or fat replacement. There is no disclosure of the preparation of a browning agent from the microcrystalline cellulose material.
Furthermore, U.S. Pat. No. 4,744,926 issued May 17, 1988 to Rice, assigned to Vitamins, Inc., discloses a process for extracting liquids from solids, including the extraction of colors, flavors and essences from roots, bark, leaves, flowers, and seeds. However, there is no disclosure of the production of a liquid browning agent from a delignified pulp, such as a hardwood material.
Moreover, of background interest, U.S. Pat. No. 4,511,613 issued Apr. 16, 1985 to Nicholson et al., assigned to Union Carbide Corporation, and U.S. Pat. No. 4,500,576 issued Feb. 19, 1985 to Nicholson et al., assigned to Union Carbide Corporation, each discloses a process and composition for inhibiting formation of discoloration and black spots on a cellulose food casing treated with liquid smoke. Each patent discloses the contacting of the food casing with an agent having the ability to prevent the progressive oxidation of metals, a noted cause of discoloration. The disclosed liquid smoke is derived from natural wood.
Additionally, U.S. Pat. No. 5,866,526 issued Feb. 2, 1999 to Olsen et al., assigned to Novo Nordisk A/S, discloses an enzyme preparation made from a modified enzyme selected from the group consisting of an amylase, lipase, oxidoreductase, pectinase, or hemicellulase. The enzyme preparation is disclosed as potentially useful in human food applications including baking, beer brewing, and juice preparation, and also in the preparation of animal feed. Thus, while this patent discloses the enzyme, hemicellulase, for use with food, nothing is disclosed vis-a-vis delignified wood pulp.
Lastly, of background interest is U.S. Pat. No. 5,681,603 issued Oct. 28, 1997 to Underwood, assigned to Red Arrow Products, which discloses making a coloring/flavoring composition by contacting water insoluble tar by-product (from liquid smoke) with an alkaline solution to an end pH above 10, and then with certain non-ionic aromatic hydrocarbon-based resins.
The disclosures of all of the above-mentioned patents are incorporated herein by reference.
Nevertheless, problems still exist with attempts to obtain a browning agent that does not impart flavor characteristics even though the literature on biomass pyrolysis indicates that the phenols are essentially a product of lignin degradation while the acids and carbonyls are obtained from degradation of cellulose and hemicellulose.
Surprisingly, the present inventors have discovered how to obtain browning/coloring solutions of low phenol and acid content relative to carbonyls content (which solutions provide for high stain/browning- low/altered flavor solutions) by pyrolysis of delignified hardwood pulp.